Abstract
ABSTRACTThe COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is ongoing and has shown the community that flexible methods for rapidly identifying and screening candidate antivirals are needed. Assessing virus-neutralizing activity of human serum to monitor population immunity and response to infection and vaccination is key to pandemic control. We developed a virus neutralization platform strategy that relies only on bioinformatic and genetic information of the virus of interest. The platform uses viral envelope glycoprotein cDNAs to set up an assay that mimics multicycle infection but is safe and, therefore, amenable to biosafety level 2 (BSL2) conditions for viruses that require BSL3 facilities (e.g., SARS-CoV-1 and SARS-CoV-2). As a complement to this platform, we present a new cell-based immunofluorescent (CBI) assay that uses SARS-CoV-2 spike protein (S)-expressing cells to accurately measure the neutralization potential of human sera and is readily adaptable to variants of concern. These methods should be useful additions to the tools for assessing antiviral immunity, whether acquired via natural infection or vaccines.IMPORTANCE Assays for rapid biosafety level 2 (BSL2) evaluation of neutralizing properties of antibodies acquired via natural infection or through vaccination is urgently needed. Here, we propose a combinatorial approach in which sera are screened for SARS-CoV-2 spike protein (S) binding using a cell-based immunofluorescent (CBI) assay, and positive samples are further evaluated in a pseudotyped viral multicycle infection-mimicking protocol under BSL2 conditions.
Highlights
The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is ongoing and has shown the community that flexible methods for rapidly identifying and screening candidate antivirals are needed
As a complement to the multicycle replication assay for assessing patient sera, we developed a cell-based immunofluorescent assay using S-expressing cells that rapidly measures neutralization activity of human sera under biosafety level 2 (BSL2) conditions
In adapting our multicycle infection (MCI) mimicking assay [8] to SARS-CoV-1 and SARS-CoV-2, we found that the SARS-CoV-2 wild-type S protein permitted robust quantitation without any modification
Summary
The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is ongoing and has shown the community that flexible methods for rapidly identifying and screening candidate antivirals are needed. Assessing virus-neutralizing activity of human serum to monitor population immunity and response to infection and vaccination is key to pandemic control. As a complement to this platform, we present a new cell-based immunofluorescent (CBI) assay that uses SARS-CoV-2 spike protein (S)-expressing cells to accurately measure the neutralization potential of human sera and is readily adaptable to variants of concern. These methods should be useful additions to the tools for assessing antiviral immunity, whether acquired via natural infection or vaccines. Methods for screening the neutralizing properties of human sera under biosafety level two (BSL2) conditions are valuable, since live SARS-CoV-2 requires scarce biosafety level three (BSL3) facilities
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